Was driving home about 10:00 PM the other night and after I got about 3/4 of a mile down the road the headlights cut out (BTW It was pitch dark out and I have no dash or interior lights). Pulled over the the side of the road and the headlights came back on, and the situation kept repeating until I got home.

I was thinking it was either the dimmer switch or a short? maybe a ground Haven't looked to deep into it yet.

 

Your headlight switch is old and its internal circuit breaker is causing it to cycle on and off.

Either replace it or install a headlight relay harness to remove the load from the switch. The relay harness will only use the headlight switch voltage to energize the relays which, in tun, connect the headlights directly to battery voltage. You'll have brighter lights to boot!

Make a harness yourself or buy one from LMC for about $30.

Scroll down to the electrical section in this post for DIY info: https://www.ford-trucks.com/forums/1...l#post13139591

 

Headlights rarely get used so I think I'll get a new switch. Thank you

 

Your call but the better value is the headlight relay harness... it's only $6 more than a switch.

 

So reading the post it is interesting to find out the ignition switch has a breaker built in. My problem only occurs with the use of high beams. headlights and dash lights all turn off then come back on after abought a minute. So is a bad connection causing a heat problem that trips the breaker. It only last a minute or so then on for a little then off. Problem goes away with switch back to low beam. 1 minute does seam like a long time when going down the freeway at 70 mph.

Will check on the relay option.

 

It's not a bad plan to replace the floor switch along with the headlight switch too, can't be far behind. Was thinking about a relay for my rig but found once I got the electrical system up to spec the headlights aren't too bad, and my night vision ain't what it used to be. I am running some Ford script repros that seem brighter than regular sealed beams.

 

Dimmer switch contacts corrode, so when you step on the switch to go from low to high beam, the headlights cut out. This is a very common problem on all 1960/70's Ford vehicles.

 

67 Dually I highly recommend this article Whiter Whites, Brighter Brights | Ford Trucks

This one has been around since mid 90s. This will stop the lights going off, a new switch may not.


John

 

First of all, this thread is almost a year old.

Secondly, The OP doesn't tell us what sort of truck he's talking about, so it's hard to know which schematic to study.

Third, (specifically to rich1brad) it isn't the Ignition switch with the self-resetting circuit breaker, it's the Headlight switch. BTW, if you want more help with your electrical problem(s), let us know what kind of truck you're talking about. Also, it would probably be a good idea to start a new thread about it.

Fourth, Tedster9, I change about three light switches for each dimmer switch. I've found that the rheostats wear out a lot faster than the dimmer switches do. I will admit, however, that changing out the dimmer switch is easy and fairly cheap.

Fifth, I've never had a dimmer switch failure lead to intermittent headlight operation - it's always led to having the headlight beams being stuck on "High" or "Low" and then unable to change to the other setting.

It seems to me that a direct short would blow a fuse, melt the resistance wire or something similar -- in any case, something relatively permanent. Can't see how the lights would automatically come back on afterwards.

An intermittent open in the wiring makes sense. Good luck on finding that. Heat-related cycling of the self-resetting circuit breaker would cause an intermittent open in the circuitry, so it sounds like a prime candidate. I'd check the light switch connector for signs of overheated contacts.

 

Must be all the salt that gets used on the roads around here compared to Cali. I never claimed the dimmer leads to intermittent as the OP described, just that it's a good practice to change them buggers out.

All the current for the lights goes through that switch too. Yep, they are cheap enough it's not worth worrying about and only takes a minute.

 

+1 VERY COMMON had this happen to both my 65 and 66 mustang with same style switch . Just don't get the cheapo autozone/pepboys replacement they are crap.

 

My bad on the switch, i meant light switch. I am familiar with the dimmer switch kind of problems and it is fine, because the lights go to high beam and work great for a while then all lights in the dash and headlights go out, so it is likely the breaker in the light switch. It was my first suspect so i quickly started pressing the dimmer switch thinking that was the problem, to no effect. As i was getting ready to pull off the road everything just came back on. So I did not use the high beams anymore on that trip.

I knew it was an old post, but used the search function to find a thread related to my problem. Did not want to start a post if there was already something out there. I really appreciate this site, and have no problem filtering through all the suggestions right or wrong, they still save me a lot of time.

Thanks everyone.

 

On my 67 250 just had a similar problem, although it was more like the headlights were "pulsing" on and off after being on for about a minute.

Ended up finding the harness on the pass side had slipped under the battery, and that caused the wires to be worn through and causing an intermittent short.

Cleaned them up, resealed then individually and shrinkwrapped them, problem solved.

 

Apparently I don't have sufficient privileges to see this page...

 

That's odd, neither do I, and I used the link yesterday with no issue.